1. Field of the Invention and Related Art Statement
The present invention relates to all automatic chemical analyzer, and more particularly to an automatic chemical analyzer comprising a reagent delivering means for delivering different kinds of reagents without contamination.
There has been proposed an automatic chemical analyzer which can measure a plurality of substances contained in samples. Such an analyzer is usually called a multi-item analyzer. In such a multi-item analyzer, it is required to deliver various kinds of reagents without contamination therebetween.
In Japanese Patent Application Laid-open Publication Kokai Sho 55-140156, there is described a known multi-item analyzer in which a delivery probe and a conduit connected thereto are washed by conducting water or a diluent in time intervals between successive delivering operations which might cause the contamination. In Japanese Patent Publication No. 59-20089, there is also disclosed a known multi-item analyzer in which after discharging a given amount of a reagent through a reagent probe, a given amount of a diluent is discharged from the same reagent probe to wash an inner wall of the reagent probe.
In the known multi-item analyzers explained above, the reagent probe is washed at time intervals between successive delivering operations. That is to say, the inner wall of the reagent probe is washed by discharging the water or diluent through the reagent probe and the outer wall of the probe is washed by immersing a tip of the probe into a washing water. It is apparent that such a washing operation is time-consuming, so that the analyzing speed is limited. Moreover, the washing operation requires a large amount of the washing water or diluent, and thus the running cost of the analyzer may be expensive. Particularly, a latex type reagent might be adhered to the reagent probe strongly, so that it is rather difficult to remove the reagent adhered to the reagent probe only by washing and the contamination could not be avoided effectively. Nowadays the measuring sensitivity of the analyzer has become very high, and therefore if even a very small amount of the reagent remains on the reagent probe, there might be produced a serious problem due to the contamination. Particularly, the influence of the contamination is manifest in the immunological analysis.
In order to wash the outer wall of the reagent probe effectively, it has been proposed to limit the amount of descending movement of the probe, so that every time a predetermined length of the probe tip is inserted into the reagent. However, this measure requires a much more complicated construction and the cost of the analyzer becomes high.
There has also been proposed a multi-item analyzer in which a probe is detachably secured to a tip of a reagent delivery nozzle and after a reagent has been delivered, the probe is removed from the tip of the reagent nozzle and a new probe is set to the tip of the reagent nozzle. In this known analyzer, the problem of contamination between different kinds of reagents can be avoided completely, because the reagent is sucked exclusively into the detachable probe. However, a large number of probes have to be arranged in such a manner that the reagent delivery nozzle can pick them up successively. Therefore, the analyzer may be complicated in construction, large in size and expensive in cost. Further the used probes are wasted, and thus the running cost of analysis becomes very high.
It should be noted that the above explained problem of contamination also occurs in a sample probe for delivering successive different samples into reaction vessels. That is to say, in almost all known analyzers, the samples are delivered with the aid of a single sample probe and the sample probe is washed at time intervals between the deliveries of different samples in order to avoid contamination between the samples.